The invention relates to a device on a draw frame having a drafting system for textile fibre slivers with weighting of the upper rolls of the drafting system. There are known draw frames with a drafting system that comprises roll pairs arranged one behind the other, the pairs having lower and upper rolls. The rotating journals at the ends of the upper roll are mounted by means of bearing elements and the bearing elements each have at least one deep-groove ball bearing having an immovable outer housing (outer ring) and an internal rotational body (inner ring).
In a known drafting system described in German Patent Specification No. 968 448, a rolling-element bearing arrangement is housed on each side of the presser roll in a special bearing housing which can be removed from the journals of the presser roll. For each journal there is provided in the bearing housing at least one rolling-element bearing for absorbing the roll weighting (transverse weighting). The rolling-element bearing is in the form of a needle bearing, roller bearing or ball bearing. A second rolling-element bearing or plain bearing is present to absorb the roll traction (axial shear forces). The presser roll is provided with press-fitted journals at both ends.
In accordance with a first embodiment, bearing housings each contain two roller bearings, the journals of the presser roll being mounted directly on the rollers. The roller bearings have an immovable outer ring which is fixed in the bearing housing. The roller bearings form separate components. When the bearing housings are being removed, the rollers have to be secured against falling out. A further construction comprises a needle bearing for absorbing the presser roll weighting and a plain bearing for absorbing the roll traction. In the same way as the roller bearings, the needle bearings form a separate component having an outer ring, and the needles have to be secured against falling out during demounting. In accordance with a third proposal having a roller bearing for absorbing the presser roll weighting, the bearing housing of the presser roll with its bearings can, by means of a screw connection, be removed from the roll journal for the purpose of applying a covering or for grinding the covering or for lubricating the bearings. Once they have been pulled outwards, the bearing housings can be unscrewed from the body of the roll. The body of the roll and the journals form a unit. In accordance with a fourth concept, a presser roll having a ball bearing for absorbing the weighting and the roll shear and a needle bearing for absorbing the roll traction are provided. The ball bearing is a separate component having its own outer and inner rings which are supported against the bearing housing and the journal, respectively. A particular problem is that the bearing housing of the presser roll here cannot be removed from the journal. A fifth embodiment provides a presser roll having a roller bearing for absorbing the roll weighting and a ball bearing for absorbing the roll traction and roll shear. The roller bearing and the ball bearing form separate components, which is expensive. In the same way as in the described third construction, the bearing housing of the presser roll is arranged on the journal so as to be removable by means of displacement and a screw connection.